Optical waveguide device and fabricating method thereof

ABSTRACT

Optical waveguide device has waveguide strip-shaped in the depth direction of the drawing and protruding from peripheral portion. A core (not illustrated) is disposed inside waveguide. Wall to be cut is integrated with waveguide to form one core layer. No unevenness occurs in a cutting line of wall indicated with broken line. Accordingly, high-precision cutting is enabled by cutting wall along the cutting line.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a division of application Ser. No. 10/387,130, filedMar. 13, 2003, now pending, and based on Japanese Patent Application No.2002-068967, filed Mar. 13, 2002, by Taro Kaneko, which is incorporatedherein by reference in its entirety. This application claims onlysubject matter disclosed in the parent application and thereforepresents no new matter.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical waveguide device such as anarrayed waveguide grating (AWG), and a fabricating method thereof, andin particular, to an optical waveguide device and a fabricating methodthereof suitable for cutting or processing a portion formed with a lightguiding core.

2. Description of the Related Art

With the remarkable development of communications technology such as theInternet, it has rapidly been required that optical waveguide devices beenhanced in function, and hybrid packaging of optical waveguide deviceshas also been actively performed. Such hybrid packaging requireshigh-precision cutting of the device at a predetermined portion forjoining the optical waveguide devices, or each kind of processing suchas provision of a groove or space in the device for incorporating othercomponents. Also, even when such hybridization is not performed,components such as optical fiber arrays are often joined to the end faceof the optical waveguide device for light input/output. To this end,cutting of the end face or predetermined portion of these opticalwaveguide devices cut out from the wafer is performed.

However, when such cutting of the optical waveguide devices isperformed, chippings and recesses occur in the end face of the opticalwaveguide in the event that its upper surface is uneven. Consequently,the optical connection with a component arranged in contact with the endface is not satisfactorily performed. Prior to the examination of theshape of the cut surface, the occurrence of unevenness in the uppersurface of the optical waveguide device is explained.

FIG. 1 illustrates an example of a production process when a core and acladding are formed over a substrate. First, as illustrated in FIG. 1A,substrate 1 such as silicon (Si) is prepared. Then, as illustrated inFIG. 1B, substrate 1 is coated on one side with lower cladding layer 2.Further, as illustrated in FIG. 1C, lower cladding layer 2 is coatedwith core layer 3.

FIG. 1D illustrates a processing step for removing an unwanted portionof core layer 3. Core layer 3 is applied with photoresist 4, coveredwith photo-mask 5 and irradiated with ultraviolet light 6. Pattern 7matched with a portion which remains as a core is formed in photo-mask5, so that in photoresist 4 only an area where the portion remains asthe core, or an area except the portion which remains as the core isirradiated with the ultraviolet light. FIG. 1E illustrates a statesubsequent to the development of photoresist 4. Photoresist 4A is onlythe portion which remains as the core.

FIG. 1F illustrates a state subsequent to etching. The etching removes aportion of core layer 3 on which photoresist 4A is absent, so that onlyrequired core portion 3A remains. FIG. 1G illustrates a state subsequentto the removal of photoresist 4A by a chemical.

Thereafter, as illustrated in FIG. 1H, lower cladding layer 2 and coreportion 3A are coated with upper cladding layer 8. In this coatingprocess, since the portion to be the cladding is deposited from the topof this diagram, upper cladding layer 8 is higher on the portioncorresponding to protruding core portion 3A than on the other portionthereof in FIG. 1G.

FIGS. 2-4 illustrate some of cross-sectional structures of opticalwaveguide devices. In these figures, the same characters as FIG. 1denote like portions. FIG. 2 illustrates an optical waveguide deviceproduced by the production process explained in FIG. 1, and which iscalled the embedded waveguide.

FIG. 3 illustrates an optical waveguide device called the ridgewaveguide, in which portion 21A of core layer 21 formed on claddinglayer 2 formed on substrate 1 protrudes. Portion 21A serves as the core.FIG. 4 illustrates an optical waveguide device called the strip loadedwaveguide, in which core layer 22 formed on cladding layer 2 ispartially loaded with core 23.

Although there are some other different production processes for opticalwaveguide devices, cores 3A, 21A, and 23 of the optical waveguidedevices illustrated in FIGS. 2-4 are formed even higher than theperiphery. Therefore, forming upper cladding layer 8 in the followingstep makes the portion on cores 3A, 21A, and 23 higher than the otherportion.

The prior-art processing will hereinafter be explained concerning thecutting of such optical waveguide devices.

FIGS. 5 and 6 illustrate an example of forming a groove by cuttinghalfway through a substrate of an optical waveguide device. Thisproposal shown in Japanese unexamined patent publication No. 11-23873processes the groove in the optical waveguide device. As illustrated inFIG. 5, the 1st step forms groove 16 by etching in waveguide 15 made ofcore 12 and claddings 13 and 14 formed on substrate 11. As illustratedin FIG. 6, the 2nd step also forms groove 16 in substrate 11 bymechanical cutting with narrower blade 17 than groove 16.

This proposal forms the groove against hard waveguide 15 by etching inthe 1 st step. Accordingly, damage to blade 17 is reduced. Also, sincegroove 16 is formed in waveguide 15 by etching, the chipping ofwaveguide 15 is reduced. Also, the positional control of blade 17 isdisclosed in Japanese unexamined patent publication No. 2000-275450.

Now, the core and claddings are present in the waveguide on top of theoptical waveguide device, and the unevenness is present between the coreand claddings and the upper surface portion of the substrate beingpositionally matched thereto, as explained above. Cutting such an unevenportion or groove therein causes deformation in the shape of theprocessed end face, and degradation in the optical characteristics.

FIG. 7 illustrates a near end of an optical waveguide device, while FIG.8 is a top view of the optical waveguide illustrated in FIG. 7. Opticalwaveguide device 31 shown in these figures is made of substrate 32 andwaveguide 33, wherein waveguide 33 protrudes upwards. Optical waveguidedevice 31 is cut in a slightly inner portion from one end along brokenline 35 perpendicular to the top surface of the substrate (see FIG. 8).Cutting techniques by reactive ion etching and by a blade are examined.

FIG. 9 illustrates an outline of a production process by reactive ionetching. FIG. 9A illustrates a side view of optical waveguide device 31prior to processing. Optical waveguide device 31 is applied withphotoresist 41 (FIG. 9B), covered with photo-mask 42, and irradiatedonly on broken line 35 with ultraviolet light 43 (FIG. 9C) for patterntransfer. Then by the development of photoresist 41, photoresist 41 isselectively removed with respect to the UV-irradiated line.

Thereafter, a gas is changed by the application of high frequency powerinto a plasma state to produce accelerated plus ions to collide with theoptical waveguide device, and thereby cause reactive ion etching (RIE).The introduced gas uses a compound containing a halogen such as fluorineor chlorine to be reactive with the substrate material and tend toproduce a volatile substance. Accordingly, the gas and substance in thecut location react to produce a volatile substance, while the processingprogresses.

FIG. 10 illustrates a manner of cutting an optical waveguide device witha blade. In this case, optical waveguide device 31 is cut along brokenline 35 (see FIG. 8) with disk-shaped blade 51 pressed thereagainst.

FIGS. 11A and 11B illustrate a change in the end face subsequent toreactive ion etching. Waveguide 33 protruding from substrate 32 isrecessed (recess 36) from the other cut surface. This recess 36 iscaused by thinner photoresist 41 on protruding waveguide 33 than on theother top surface as illustrated in FIG. 9C. That is, since protrudingwaveguide 33 tends to be etched more than the other portion, the cutportion of protruding waveguide 33 is recessed.

On the other hand, the cutting of the optical waveguide device by blade51 (shown in FIG. 10) or dicing saw tends not only to damage the bladeat the relatively hard protruding core portion, but also to causechipping in waveguide 33, as pointed out in Japanese unexamined patentpublication No. 11-23873.

FIG. 12 illustrates an example of such chipping in a waveguide. Chipping37 occurs at the end of protruding waveguide 33 from substrate 32 inFIG. 12 corresponding with FIG. 11A. Also, in the optical waveguidedevice where the core forms the protrusion while the cladding forms therecess as illustrated FIGS. 3 and 4, local stress concentration tends toselectively cause chipping in the core or cladding. Blade deformation bysuch chipping and protrusion causes a defect in the cut end face.

As explained above, in the case that the upper surface of the opticalwaveguide device is uneven, the prior art has difficulty inhigh-precision cutting thereof. This is also true for the case of theprocessing of a groove. Consequently, the problem exists of being unableto satisfactorily bond or incorporate other components to be matchedwith the processed end face and groove, and degrading the opticalcharacteristics of hybrid-packaged components or components joined toother components at the end face.

SUMMARY OF THE INVENTION

Thus, an object of the present invention is to provide an opticalwaveguide device whose core portion can be cut with high precision, or amethod of fabricating an optical waveguide device capable of being thuscut.

The foregoing and other objects of the present invention are achieved bythe following:

An optical waveguide device comprises a core for propagating light, anda member to be cut at a predetermined angle to the core, the memberbeing arranged to cross the core at the angle, and a height of themember being constant at a position where the member crosses the core.

An optical waveguide device comprises a core for propagating light; anda member having a predetermined width to be cut in its lengthwisedirection, the member being arranged to cross the core at apredetermined angle, and a height of the member being varied uniformlyat a position where the member crosses the core.

An optical waveguide device comprises a core for propagating light, anda member having a predetermined width to be cut in its lengthwisedirection, the member being connected with the core at a predeterminedangle to provide a T-shaped pattern, and a height of the member beingconstant at a position where the member is connected with the core.

An optical waveguide device comprises a core for propagating light, anda member having a predetermined width to be cut in its lengthwisedirection, the member being connected with the core at a predeterminedangle to provide a T-shaped pattern, and a height of the member beingvaried uniformly at a position where the member is connected with thecore.

In the above optical waveguide devices, the core is the same in materialas the member.

In the above optical waveguide devices, the core is integrated with themember.

In the above optical waveguide devices, the core and the member arecovered with a cladding.

In the above optical waveguide devices, the core and the member arecovered at least on a side of a substrate with a cladding.

In the above optical waveguide devices, the core and the member areformed on a core layer which is the same in material as the core.

In the above optical waveguide devices, the core includes a plurality ofcores which are arranged in parallel with a predetermined interval; andthe member is connected in common with the plurality of cores.

In the above optical waveguide devices, the core is of a tapered shapeat an end portion thereof, with which the member is in contact.

In the above optical waveguide devices, the tapered shape of the core islarger in width, as a distance of the core is smaller relative to themember.

In the above optical waveguide devices, the tapered shape of the core issmaller in width, as a distance of the core is smaller relative to themember.

In the above optical waveguide devices, the member is arranged to crossthe core at an angle of 90°.

In the above optical waveguide devices, the member is arranged to crossthe core at an angle of 80° to 100°.

According to the above optical waveguide devices of the presentinvention, since the member with no unevenness is disposed and cut atthe end of the core through which light propagates, no local stress dueto unevenness occurs during cutting, and high-precision cutting isenabled, thereby ensuring satisfactory optical coupling between this cutsurface and another optical device opposite thereto or in contacttherewith.

Also, since the core and the member to be cut are integrated with eachother, the high-quality optical waveguide device can not only befabricated inexpensively, but optical loss due to reflection at aconnection portion can also be suppressed.

Further, since the taper is formed at the tip of the core in contactwith the member to be cut, satisfactory optical coupling is enabledbetween this cut surface and another optical device opposite thereto orin contact therewith.

Also, since the member to be cut is arranged to cross said core at anangle of 80° to 100°, light reflected at the end face of the core can beprevented from returning thereto.

A method of fabricating an optical waveguide device, comprises the stepsof: forming a cladding on a substrate; forming a core layer of a flatplate shape on the cladding; removing the core layer in a predeterminedshape at a predetermined depth to provide a member having apredetermined width to be cut in its lengthwise direction, the memberbeing arranged to cross a core for propagating light at a predeterminedangle, and a height of the member being constant at a position where themember crosses the core, while the predetermined shape excluding thecore and the member; and cutting the member in the lengthwise direction.

A method of fabricating an optical waveguide device, comprises the stepsof: forming a cladding on a substrate; forming a core layer of a flatplate shape on the cladding; removing the core layer in a predeterminedshape at a predetermined depth to provide a member having apredetermined width to be cut in its lengthwise direction, the memberbeing arranged to cross a core for propagating light at a predeterminedangle, and a height of the member being varied uniformly at a positionwhere the member crosses the core, while the predetermined shapeexcluding the core and the member; and cutting the member in thelengthwise direction.

A method of fabricating an optical waveguide device, comprises the stepsof: forming a cladding on a substrate; forming a core layer of a flatplate shape on the cladding; removing the core layer in a predeterminedshape at a predetermined depth to provide a member having apredetermined width to be cut in its lengthwise direction, the memberbeing connected with a core for propagating light at a predeterminedangle to provide a T-shaped pattern, and a height of the member beingconstant at a position where the member is connected with the core,while the predetermined shape excluding the core and the member; andcutting the member in the lengthwise direction.

A method of fabricating an optical waveguide device, comprises the stepsof: forming a cladding on a substrate; forming a core layer of a flatplate shape on the cladding; removing the core layer in a predeterminedshape at a predetermined depth to provide a member having apredetermined width to be cut in its lengthwise direction, the memberbeing connected with a core for propagating light at a predeterminedangle to provide a T-shaped pattern, and a height of the member beingvaried uniformly at a position where the member is connected with thecore, while the predetermined shape excluding the core and the member;and cutting the member in the lengthwise direction.

A method of fabricating an optical waveguide device, comprises the stepsof: forming a cladding on a substrate; forming a first core layer of aflat plate shape on the cladding; forming a second core layer on thefirst core layer; removing the second core layer in a predeterminedshape at a predetermined depth to provide a member having apredetermined width to be cut in its lengthwise direction, the memberbeing arranged to cross a core for propagating light at a predeterminedangle, and a height of the member being constant at a position where themember crosses the core, while the predetermined shape excluding thecore and the member; and cutting the member in the lengthwise direction.

A method of fabricating an optical waveguide device, comprises the stepsof: forming a cladding on a substrate; forming a first core layer of aflat plate shape on the cladding; forming a second core layer on thefirst core layer; removing the second core layer in a predeterminedshape at a predetermined depth to provide a member having apredetermined width to be cut in its lengthwise direction, the memberbeing arranged to cross a core for propagating light at a predeterminedangle, and a height of the member being varied uniformly at a positionwhere the member crosses the core, while the predetermined shapeexcluding the core and the member; and cutting the member in thelengthwise direction.

A method of fabricating an optical waveguide device, comprises the stepsof: forming a cladding on a substrate; forming a first core layer of aflat plate shape on the cladding; forming a second core layer on thefirst core layer; removing the second core layer in a predeterminedshape at a predetermined depth to provide a member having apredetermined width to be cut in its lengthwise direction, the memberbeing connected with a core for propagating light at a predeterminedangle to provide a T-shaped pattern, and a height of the member beingconstant at a position where the member is connected with the core,while the predetermined shape excluding the core and the member; andcutting the member in the lengthwise direction.

A method of fabricating an optical waveguide device, comprises the stepsof: forming a cladding on a substrate; forming a first core layer of aflat plate shape on the cladding; forming a second core layer on thefirst core layer; removing the second core layer in a predeterminedshape at a predetermined depth to provide a member having apredetermined width to be cut in its lengthwise direction, the memberbeing connected with a core for propagating light at a predeterminedangle to provide a T-shaped pattern, and a height of the member beingvaried uniformly at a position where the member is connected with thecore, while the predetermined shape excluding the core and the member;and cutting the member in the lengthwise direction.

In the above methods of fabricating an optical waveguide device, thecutting step is carried out to cut the member by means of reactive ionetching.

In the above methods of fabricating an optical waveguide device, thecutting step is carried out to cut the member by use of a dicing saw.

According to the above methods of fabricating an optical waveguidedevice of the present invention, since subsequent to forming of the corelayer of a flat plate shape on the substrate, the portion excluding thecore and the member is removed, no unevenness exists in the cuttingdirection of the member, thereby enabling high-precision cuttingthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will hereinafter bedescribed with reference to the accompanying drawings, wherein:

FIGS. 1A-1H are an explanatory step diagram illustrating an example of aproduction process when a core and a cladding are formed over asubstrate.

FIG. 2 is an explanatory diagram illustrating a cross-sectionalstructure of an embedded waveguide.

FIG. 3 is an explanatory diagram illustrating a cross-sectionalstructure of a ridge waveguide.

FIG. 4 is an explanatory diagram illustrating a cross-sectionalstructure of a strip loaded waveguide,

FIG. 5 is a cross-sectional view illustrating a prior-art proposed 1ststep of changing a processing technique according to hardness of anoptical waveguide device.

FIG. 6 is a cross-sectional view illustrating a 2nd step of the proposalshown in FIG. 5.

FIG. 7 is a perspective view of an essential portion illustrating a nearend of an optical waveguide device.

FIG. 8 is a top view of the optical waveguide illustrated in FIG. 7.

FIGS. 9A-9C are an explanatory diagram illustrating an outline of afabricating process by reactive ion etching.

FIG. 10 is an explanatory diagram illustrating a manner of cutting anoptical waveguide device with a blade.

FIGS. 11A and 11B are top and perspective views of a waveguideillustrating a change in an end face subsequent to reactive ion etching.

FIG. 12 is a top view when an optical waveguide device is cut with ablade or dicing saw.

FIG. 13 is a perspective view of an essential portion prior toprocessing of an optical waveguide device constituting an opticalwaveguide device in one embodiment of the present invention.

FIG. 14 is a top view of an optical waveguide device constituting theoptical waveguide device of the present embodiment.

FIG. 15 is a top view illustrating an optical waveguide devicesubsequent to reactive ion etching in the present embodiment.

FIG. 16 is a perspective view of an essential portion illustrating asubstrate of the optical waveguide device of the present embodiment.

FIG. 17 is a perspective view of an essential portion illustrating astate where the substrate of the optical waveguide device of the presentembodiment is coated with a lower cladding layer.

FIG. 18 is a perspective view of an essential portion illustrating astate where the lower cladding layer is uniformly formed with a corelayer in the present embodiment.

FIG. 19 is a top view of an essential portion illustrating a pattern ofa photo-mask used in the present embodiment.

FIG. 20 is a perspective view of an essential portion of the opticalwaveguide device illustrating a state subsequent to etching of the corelayer illustrated in FIG. 19 in the present embodiment.

FIG. 21 is a characteristics graph showing a relationship betweenresidual thickness of a wall to be cut and excess loss due thereto.

FIG. 22 is a top view of an essential portion illustrating a state priorto cutting of an optical waveguide device as the first modified exampleof the present invention.

FIG. 23 is a top view of an essential portion illustrating a state priorto cutting of an optical waveguide device as the second modified exampleof the present invention.

FIG. 24 is an explanatory diagram illustrating a manner of lighttransmission and reflection in the optical waveguide device subsequentto cutting in the second modified example.

FIG. 25 is a top view of an essential portion illustrating a state priorto cutting of an optical waveguide device in the third modified exampleof the present invention.

FIG. 26 is a top view of an essential portion illustrating a state priorto cutting of an optical waveguide device in the fourth modified exampleof the present invention.

FIG. 27 is a cross-sectional view illustrating a planer light-wavecircuit cut horizontally at a specified height from the substrate as anoptical waveguide device in the fifth modified example of the presentinvention.

FIG. 28 is a top view illustrating a pattern of the core prior tocutting of the optical waveguide device illustrated in FIG. 27.

FIGS. 29A and 29B are top and side views of an optical waveguide deviceillustrating an example of interposing a filter in a cut wall subsequentto cutting of two waveguides.

FIGS. 30A and 30B are top and side views of an optical waveguide deviceillustrating an example of arranging an end face of an optical fiberopposite a cut wall subsequent to cutting of a waveguide.

FIGS. 31 A and 31B are top and side views of two optical waveguidedevices illustrating an example of optical coupling of the two opticalwaveguide devices by arranging their cut walls directly opposite eachother.

FIGS. 32A and 32B are top and side views of an optical waveguide deviceillustrating an example of optical coupling of the optical waveguidedevice and an optical device such as a light emitting/receiving device.

FIGS. 33A and 33B are top and side views of an optical waveguide deviceillustrating another example of optical coupling of the opticalwaveguide device and an optical device such as a lightemitting/receiving device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 13 illustrates a state prior to cutting of an optical waveguidedevice in one example of the present invention, and corresponds to FIG.7. Optical waveguide device 101 has waveguide 103 strip-shaped in thedepth direction of the drawing and protruding from peripheral portion102, as in FIG. 7. A core (not illustrated) is disposed inside waveguide103 or in a lower portion thereof. A different aspect from FIG. 7 isthat there is formed wall to be cut (member to be cut) 106 with the sameheight as waveguide 103 as indicated with broken line (cutting line)105.

FIG. 14 is a top view of a waveguide of an optical waveguide device ofthe present invention, and corresponds to FIG. 8. As also understoodfrom FIG. 14, the cutting line indicated with broken line 105 is along atop of wall 106 to be cut. Since wall 106 to be cut has the same heightas protruding strip-shaped waveguide 103, these portions are in a Tshape as a whole.

FIG. 15 illustrates an optical waveguide device subsequent to reactiveion etching. The cutting line indicated with broken line 105 in FIG. 14has the same height in the entire area. Accordingly, a resist appliedprior to reactive ion etching has a uniform thickness at the top of wall106 to be cut. Therefore, cutting by reactive ion etching can beperformed without causing a recess as indicated with broken line 105 ofFIG. 14.

FIGS. 16-18 illustrate each essential step of a process of producingsuch an optical waveguide device. FIG. 16 illustrates substrate 111 ofthis optical waveguide device. Substrate 111 uses silicon (Si). FIG. 17illustrates a state where substrate 111 is coated with lower claddinglayer 112. FIG. 18 illustrates a state where lower cladding layer 112 isuniformly formed with core layer 113. So far, the process is exactly thesame as the prior-art process of producing an optical waveguide device.

FIG. 19 corresponds to FIG. 1D, and illustrates a pattern of aphoto-mask used for etching core layer 113 illustrated in FIG. 18.Photo-mask 121 of this embodiment is in T-shaped pattern 122 where aportion to remain as the core shields ultraviolet light. Photo-mask 121is disposed on a photoresist (not illustrated) applied to core layer 113illustrated in FIG. 18, and is irradiated with ultraviolet light.Thereafter, the photoresist is developed, and remains on core layer 113in the same pattern as T-shaped pattern 122. This is processed with achemical to etch and remove a portion of core layer 113 where thephotoresist is absent.

FIG. 20 illustrates a halfway production process of an optical waveguidedevice thus formed with T-shaped core layer 113. This is further coatedwith an upper cladding 185 to provide optical waveguide device 101 asillustrated in FIG. 13. The height of each portion of T-shaped corelayer 113 illustrated in FIG. 20 is the same. Accordingly, in the stageof coating the upper cladding, protruding strip-shaped waveguide 103 andwall 106 have exactly the same height as illustrated in FIG. 13. Thus,in the case where optical waveguide device 101 is cut along the cuttingline indicated with broken line 105 by reactive ion etching, nounevenness exists in this cut portion, and no deformation occurs in theend face during cutting. Likewise, in the case of the cutting of opticalwaveguide device 101 by a dicing saw, no chipping occurs in the endface, and the cut end face does not deform.

Now, in optical waveguide device 101 of this embodiment, subsequent tocutting, a portion of wall 106 is left with waveguide 103 joined theretoas illustrated in FIG. 15. Because this residual wall 106 may cause anoptical loss increase in optical waveguide device 101, this is examined.

FIG. 21 shows a relationship between residual thickness (μm) of wall 106to be cut and excess loss (dB) due thereto. If the residual wall 106 is,say, 5 μm, the loss increase is no more than 0.01 dB from thecharacteristics graph shown in FIG. 21. Thus, wall 106 has substantiallyno effect on the optical characteristics. Therefore, in opticalwaveguide device 101 of this embodiment, deformation of the end face canbe suppressed without any sacrifice in the optical characteristics.

FIG. 22 illustrates an essential portion of an optical waveguide deviceas the first modified example of the present invention. In this modifiedexample, a plurality of protruding strip-shaped waveguides 132 ₁-132 ₃are spaced parallel to each other on top of optical waveguide device131. Also, a protruding strip-shaped member 133 to be cut is disposed toperpendicularly cross these waveguides 132 ₁-132 ₃. Each waveguide 132₁-132 ₃ and member 133 are formed in the same manner as the aboveembodiment by etching-processing the same core layer into a desiredpattern and forming a cladding thereon. Thus, member 133 has the sameheight at any position and is flat.

In the case of the first modified example, member 133 is cut in themiddle portion as indicated with broken line 134, for example, byreactive ion etching, so that the device can be divided into two opticalwaveguide devices. Since member 133 has the flat surface, no deformationoccurs in the cut surface of the end of each waveguide 132 ₁-132 ₃.Accordingly, a fiber array not illustrated may be disposed opposite cutmember 133, thereby enabling satisfactory optical coupling.

FIG. 23 illustrates a state prior to cutting of an optical waveguidedevice in the second modified example of the present invention. Even inoptical waveguide device 141 of this modified example, a plurality ofprotruding strip-shaped waveguides 142 ₁-142 ₃ are spaced parallel toeach other on top of optical waveguide device 141. But, protrudingstrip-shaped member 143 to be cut is not perpendicular to thelongitudinal direction of these waveguides 142 ₁-142 ₃, and is inclinedat angle θ to its transverse direction, where angle θ is 80°-100°.

Even in the second modified example, each waveguide 142 ₁-142 ₃ andmember 143 are formed in the same manner as the above embodiment byetching-processing the same core layer into a desired pattern andforming a cladding thereon. Thus, member 143 has the same height at anyposition and is flat. When member 143 is cut in the middle portion asindicated with broken line 144, for example, by reactive ion etching, nodeformation occurs in the cut surface. Furthermore, the second modifiedexample can solve the problem of light returning to an incident side byreflection at the cut end face of each waveguide 142 ₁-142 ₃.

FIG. 24 illustrates a principle of avoiding an effect of return light.Light 146 progressing from waveguide 142 in the direction of member 143is transmitted through cut surface 147 of the core at broken line 144 ofFIG. 23, while partially reflected in the direction indicated by thearrow in FIG. 24. This reflected light does not return to waveguide 142,and is reflected, propagated and attenuated inside member 143.

FIG. 25 illustrates a state prior to cutting of an optical waveguidedevice in the third modified example of the present invention. Even inoptical waveguide device 151 of the third modified example, eachwaveguide 152 ₁-152 ₃ and member 153 to be cut are formed in the samemanner as the above embodiment by etching-processing the same core layerinto a desired pattern and forming a cladding thereon. Thus, member 153has the same height at any position and is flat. When member 153 is cutin the middle portion as indicated with broken line 154, for example, byreactive ion etching, no deformation occurs in the cut surface.

Furthermore, in the case of the third modified example, each waveguide152 ₁-152 ₃ has taper 155 narrower at the tip in contact with member153. Accordingly, an optical component such as a fiber array notillustrated may be disposed opposite the cut surface indicated withbroken line 154, thereby enabling satisfactory optical coupling viamember 153, although depends upon the shape of taper 155.

FIG. 26 illustrates a state prior to cutting of an optical waveguidedevice in the fourth modified example of the present invention. Even inoptical waveguide device 161 of the fourth modified example, eachwaveguide 162 ₁-162 ₃ and member 163 to be cut are formed in the samemanner as the above embodiment by etching-processing the same core layerinto a desired pattern and forming a cladding thereon. Thus, member 163has the same height at any position and is flat. When member 163 is cutin the middle portion as indicated with broken line 164, for example, byreactive ion etching, no deformation occurs in the cut surface.

Furthermore, in the case of the fourth modified example, each waveguide162 ₁-162 ₃ has taper 165 wider at the tip in contact with member 163.Accordingly, an optical component such as a fiber array not illustratedmay be disposed opposite the cut surface indicated with broken line 164,thereby enabling satisfactory optical coupling via member 163 althoughdepends upon the shape of taper 165.

Also, although in these modified examples, the tip of each waveguide 152₁-152 ₃ and 162 ₁-162 ₃ is in the taper shape, it may be in theexponential or quadric shape, or combination thereof.

FIG. 27 illustrates a planer light-wave circuit cut horizontally at aspecified height from the substrate as an optical waveguide device inthe fifth modified example of the present invention. In planerlight-wave circuit 171, single mode input optical fiber 172 and outputoptical fiber 173 are optically-coaxially connected by glass block 174for fixation to respective first and second optical waveguides 176 and177 formed on device body 175. Groove 178 is provided near a convergingpoint of first and second optical waveguides 176 and 177, and dielectricmultilayer film 179 is inserted in groove 178 as a filter, and fixed byan adhesive. Third optical waveguide 181 formed opposite first andsecond optical waveguides 176 and 177 is in the same optical axis asfirst optical waveguide 176. Dielectric multilayer film 179 reflects1.55 μm light, and transmits 1.3 μm light. Third optical waveguide 181forks on the way, and laser diode 182 is disposed at one end of thefork, while photodiode 183 disposed at the other end.

In such planer light-wave circuit 171, 1.3 μm and 1.55 μmmultiwavelength light from single mode input optical fiber 172 entersfirst input/output optical waveguide 176. 1.55 μm light is reflected atdielectric multilayer film 179 and output from second optical waveguide177 to output optical fiber 173. 1.3 μm light is transmitted throughdielectric multilayer film 179, divided into two at the fork of thirdoptical waveguide 181, and coupled to photodiode 183. Also, laser diode182 is disposed at the other end of the fork. Such planer light-wavecircuit 171 is disclosed in Japanese unexamined patent publication No.2001-249247, for example.

FIG. 28 illustrates a pattern of the core prior to the cutting of theoptical waveguide device illustrated in FIG. 27. At the left end of FIG.28 of each protruding strip-shaped waveguide 191 and 192 correspondingto first and second optical waveguides 176 and 177 of FIG. 27 is formedwall 193 with the same height as them to be cut. Wall 193 is cut alongbroken line 194 by a dicing saw and then ground to be joined to glassblock 174 illustrated in FIG. 27.

Also, slightly thick wall 196 to be cut is formed on the converging sideof waveguides 191 and 192 in such a manner as to sandwich the end ofwaveguide 195 corresponding to third optical waveguide 181 of FIG. 27.Wall 196 to be cut has the same height as each waveguide 191, 192 and195. Wall 196 is cut along two parallel broken lines 197 and 198 byreactive ion etching or a dicing saw. Likewise, walls 201 and 202 to becut are provided at positions where laser diode 182 and photodiode 183are embedded respectively, and walls 201 and 202 are cut along brokenlines 203 and 204 respectively.

Further, although the core and the member to be cut, formed of the samematerial as the core, have the same height in the above embodiment andmodified examples, the member or portion to be cut only has to be eveni.e. flat in the cutting direction. Therefore, the top surface of thewall to be cut does not have to be the same in height in every portion,but may be uniformly inclined in the cutting direction, or in thedirection perpendicular thereto provided that light progression is notparticularly affected. Also, although the cutting of the portionprotruding from the periphery has been examined in the above embodimentand modified examples, the present invention may likewise be applied tocutting of a portion recessed from the periphery.

Also, although the optical coupling between the cut wall and anothercomponent has been briefly explained in the fifth modified example,examples other than this will hereinafter be shown.

FIGS. 29A and 29B are top and side views of an optical waveguide deviceillustrating an example of interposing a filter in a cut wall subsequentto cutting of two waveguides. Cut walls 304 and 305 connected to a pairof waveguides 302 and 303 formed on device body 301 are formed bycutting a wall at a specified width and depth with a dicing saw. In agroove produced by this is interposed filter 306.

FIGS. 30A and 30B are top and side views of an optical waveguide deviceillustrating an example of arranging an end face of an optical fiberopposite a cut wall subsequent to cutting of a waveguide. A portion ofcut wall 313 corresponding to the core of waveguide 312 formed on devicebody 311 is disposed opposite core tip 315 of optical fiber 314, therebyoptically coupling both.

FIGS. 31A and 31B are top and side views of two optical waveguidedevices illustrating an example of optical coupling of the two opticalwaveguide devices by arranging their cut walls directly opposite eachother. In this example, cut walls 325 and 326 connected to waveguides323 and 324 of two optical waveguide devices 321 and 322 are disposedopposite each other so that their respective core positions are matchedto each other. Although it is illustrated that optical waveguide devices321 and 322 has one respective waveguide 323 and 324, a plurality ofoptical waveguides may be provided for each optical waveguide device 321and 322, in which case these optical waveguides are optically coupled atthe same time.

FIGS. 32A and 32B are top and side views of an optical waveguide deviceillustrating an example of optical coupling of the optical waveguidedevice and an optical device such as a light emitting/receiving device.Cut wall 333 connected to waveguide 332 of optical waveguide device 331is optically coupled to optical device 334 disposed directly on the samesubstrate.

FIGS. 33A and 33B are top and side views of an optical waveguide deviceillustrating another example of optical coupling of the opticalwaveguide device and an optical device such as a lightemitting/receiving device. In this example, cut wall 343 connected towaveguide 342 of optical waveguide device 341 is optically coupled tooptical device 346 disposed directly on subcarrier oscillator 345.

Also, an example of arranging an optical device such as a lightemitting/receiving device in a recess of a substrate is illustrated inthe fifth modified example. Thus, the optical waveguide device of thepresent invention can employ each kind of form of optical coupling.

Although the invention has been described with respect to the specificembodiments for complete and clear disclosure, the appended claims arenot to be thus limited but are to be construed as embodying allmodifications and alternative constructions that may occur to oneskilled in the art which fairly fall within the basic teaching hereinset forth.

1. An optical waveguide device, comprising: a core for propagatinglight, said core formed on a substrate; and a unitary member having apredetermined width, and having a cut in its lengthwise direction, saidmember being connected with said core at a predetermined angle, and aheight of said member being constant and equal to a height of said coreat a position where said member is connected with said core, said cutextending though said substrate.
 2. An optical waveguide device,according to claim 1, wherein said core is the same in material as saidmember.
 3. An optical waveguide device, according to claim 2, whereinsaid core is fabricated to integrate with said member at a commonfabricating step.
 4. An optical waveguide device, according to claim 3,wherein said core and said member are covered with a cladding.
 5. Anoptical waveguide device, according to claim 3, wherein said core andsaid member are covered at least on a side of a substrate with acladding.
 6. An optical waveguide device, according to claim 1, whereinsaid core and said member are formed on a core layer which is the samein material as said core.
 7. An optical waveguide device, according toclaim 1, wherein said member is arranged to cross said core at an angleof 90°.
 8. An optical waveguide device, according to claim 1, whereinsaid member is arranged to cross said core at an angle of 80° to 100°.9. An optical waveguide device, comprising: a core for propagatinglight; and a unitary member having a predetermined width to be cut inits lengthwise direction, said member being connected with said core ata predetermined angle, and a height of said member being constant at aposition where said member is connected with said core, wherein saidcore includes a plurality of cores which are arranged in parallel with apredetermined interval; and said member is connected in common with saidplurality of cores.
 10. An optical waveguide device. comprising: a corefor propagating light, said core formed on a substrate: and a unitarymember having a predetermined width, and having a cut in its lengthwisedirection, said member being connected with said core at a predeterminedangle, and a height of said member being constant at a position wheresaid member is connected with said core, said cut extending though saidsubstrate, wherein said core is of a tapered shape at an end portionthereof, with which said member is in contact.
 11. An optical waveguidedevice, according to claim 10, wherein said tapered shape of said corehas an outward taper toward said member.
 12. An optical waveguidedevice, according to claim 10, wherein said tapered shape of said corehas an inward taper toward said member.
 13. A method of fabricating anoptical waveguide device, comprising the steps of: forming a cladding ona substrate; forming a core layer of a flat plate shape on saidcladding; removing said core layer in a predetermined shape at apredetermined depth to provide a member having a predetermined width tobe cut in its lengthwise direction, said member being connected with acore for propagating light at a predetermined angle to provide aT-shaped pattern, and a height of said member being constant at aposition where said member is connected with said core, while saidpredetermined shape excluding said core and said member; and cuttingsaid member in a direction parallel to said lengthwise direction.
 14. Amethod of fabricating an optical waveguide device, according to claim13, wherein said cutting step is carried out to cut said member by meansof reactive ion etching.
 15. A method of fabricating an opticalwaveguide device, according to claim 13, wherein said cutting step iscarried out to cut said member by use of a dicing saw.
 16. A method offabricating an optical waveguide device, comprising the steps of:forming a cladding on a substrate; forming a first core layer of a flatplate shape on said cladding; forming a second core layer on said firstcore layer; removing said second core layer in a predetermined shape ata predetermined depth to provide a member having a predetermined widthto be cut in its lengthwise direction, said member being connected witha core for propagating light at a predetermined angle to provide aT-shaped pattern, and a height of said member being constant at aposition where said member is connected with said core, while saidpredetermined shape excluding said core and said member; and cuttingsaid member in a direction parallel to said lengthwise direction.
 17. Amethod of fabricating an optical waveguide device, according to claim16, wherein said cutting step is carried out to cut said member by meansof reactive ion.
 18. A method of fabricating an optical waveguidedevice, according to claim 16, wherein said cutting step is carried outto cut said member by use of a dicing saw.